Journal bearings may have one or more inlets and/or grooves/features in the bore. Generally, the configuration and number of features affect both the static and dynamic performance of the bearing. Compared to a standard cylindrical bore bearing, profiled journal bearings, examples of which include but are not limited to elliptical, multi-lobe taper land, and offset bore bearings may be more stable due to lobes/features in the bore of the bearing. However, because such a bearing is a fixed profile bearing, its performance film thickness, maximum bearing temperature, and stability) is typically optimized for one or just a few loading conditions. Accordingly, when the load changes (e.g., direction, magnitude, etc.) it is common for the bearing performance to degrade. Furthermore, a profiled journal bearing may also exhibit instabilities like a standard cylindrical bore bearing under certain operating conditions.
Examples of journal bearings are shown in U.S. Pat. Nos. 6,966,700; 6,547,438; 5,480,234 and 4,097,094 and U.S. patent application Ser. No. 12/708,439, all of which are incorporated by reference herein in their entireties.